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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _FUTEX_H
3#define _FUTEX_H
4
5#include <linux/futex.h>
6#include <linux/rtmutex.h>
7#include <linux/sched/wake_q.h>
8
9#ifdef CONFIG_PREEMPT_RT
10#include <linux/rcuwait.h>
11#endif
12
13#include <asm/futex.h>
14
15/*
16 * Futex flags used to encode options to functions and preserve them across
17 * restarts.
18 */
19#ifdef CONFIG_MMU
20# define FLAGS_SHARED 0x01
21#else
22/*
23 * NOMMU does not have per process address space. Let the compiler optimize
24 * code away.
25 */
26# define FLAGS_SHARED 0x00
27#endif
28#define FLAGS_CLOCKRT 0x02
29#define FLAGS_HAS_TIMEOUT 0x04
30
31#ifdef CONFIG_FAIL_FUTEX
32extern bool should_fail_futex(bool fshared);
33#else
34static inline bool should_fail_futex(bool fshared)
35{
36 return false;
37}
38#endif
39
40/*
41 * Hash buckets are shared by all the futex_keys that hash to the same
42 * location. Each key may have multiple futex_q structures, one for each task
43 * waiting on a futex.
44 */
45struct futex_hash_bucket {
46 atomic_t waiters;
47 spinlock_t lock;
48 struct plist_head chain;
49} ____cacheline_aligned_in_smp;
50
51/*
52 * Priority Inheritance state:
53 */
54struct futex_pi_state {
55 /*
56 * list of 'owned' pi_state instances - these have to be
57 * cleaned up in do_exit() if the task exits prematurely:
58 */
59 struct list_head list;
60
61 /*
62 * The PI object:
63 */
64 struct rt_mutex_base pi_mutex;
65
66 struct task_struct *owner;
67 refcount_t refcount;
68
69 union futex_key key;
70} __randomize_layout;
71
72/**
73 * struct futex_q - The hashed futex queue entry, one per waiting task
74 * @list: priority-sorted list of tasks waiting on this futex
75 * @task: the task waiting on the futex
76 * @lock_ptr: the hash bucket lock
77 * @key: the key the futex is hashed on
78 * @pi_state: optional priority inheritance state
79 * @rt_waiter: rt_waiter storage for use with requeue_pi
80 * @requeue_pi_key: the requeue_pi target futex key
81 * @bitset: bitset for the optional bitmasked wakeup
82 * @requeue_state: State field for futex_requeue_pi()
83 * @requeue_wait: RCU wait for futex_requeue_pi() (RT only)
84 *
85 * We use this hashed waitqueue, instead of a normal wait_queue_entry_t, so
86 * we can wake only the relevant ones (hashed queues may be shared).
87 *
88 * A futex_q has a woken state, just like tasks have TASK_RUNNING.
89 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
90 * The order of wakeup is always to make the first condition true, then
91 * the second.
92 *
93 * PI futexes are typically woken before they are removed from the hash list via
94 * the rt_mutex code. See futex_unqueue_pi().
95 */
96struct futex_q {
97 struct plist_node list;
98
99 struct task_struct *task;
100 spinlock_t *lock_ptr;
101 union futex_key key;
102 struct futex_pi_state *pi_state;
103 struct rt_mutex_waiter *rt_waiter;
104 union futex_key *requeue_pi_key;
105 u32 bitset;
106 atomic_t requeue_state;
107#ifdef CONFIG_PREEMPT_RT
108 struct rcuwait requeue_wait;
109#endif
110} __randomize_layout;
111
112extern const struct futex_q futex_q_init;
113
114enum futex_access {
115 FUTEX_READ,
116 FUTEX_WRITE
117};
118
119extern int get_futex_key(u32 __user *uaddr, bool fshared, union futex_key *key,
120 enum futex_access rw);
121
122extern struct hrtimer_sleeper *
123futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout,
124 int flags, u64 range_ns);
125
126extern struct futex_hash_bucket *futex_hash(union futex_key *key);
127
128/**
129 * futex_match - Check whether two futex keys are equal
130 * @key1: Pointer to key1
131 * @key2: Pointer to key2
132 *
133 * Return 1 if two futex_keys are equal, 0 otherwise.
134 */
135static inline int futex_match(union futex_key *key1, union futex_key *key2)
136{
137 return (key1 && key2
138 && key1->both.word == key2->both.word
139 && key1->both.ptr == key2->both.ptr
140 && key1->both.offset == key2->both.offset);
141}
142
143extern int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
144 struct futex_q *q, struct futex_hash_bucket **hb);
145extern void futex_wait_queue(struct futex_hash_bucket *hb, struct futex_q *q,
146 struct hrtimer_sleeper *timeout);
147extern void futex_wake_mark(struct wake_q_head *wake_q, struct futex_q *q);
148
149extern int fault_in_user_writeable(u32 __user *uaddr);
150extern int futex_cmpxchg_value_locked(u32 *curval, u32 __user *uaddr, u32 uval, u32 newval);
151extern int futex_get_value_locked(u32 *dest, u32 __user *from);
152extern struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, union futex_key *key);
153
154extern void __futex_unqueue(struct futex_q *q);
155extern void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb);
156extern int futex_unqueue(struct futex_q *q);
157
158/**
159 * futex_queue() - Enqueue the futex_q on the futex_hash_bucket
160 * @q: The futex_q to enqueue
161 * @hb: The destination hash bucket
162 *
163 * The hb->lock must be held by the caller, and is released here. A call to
164 * futex_queue() is typically paired with exactly one call to futex_unqueue(). The
165 * exceptions involve the PI related operations, which may use futex_unqueue_pi()
166 * or nothing if the unqueue is done as part of the wake process and the unqueue
167 * state is implicit in the state of woken task (see futex_wait_requeue_pi() for
168 * an example).
169 */
170static inline void futex_queue(struct futex_q *q, struct futex_hash_bucket *hb)
171 __releases(&hb->lock)
172{
173 __futex_queue(q, hb);
174 spin_unlock(&hb->lock);
175}
176
177extern void futex_unqueue_pi(struct futex_q *q);
178
179extern void wait_for_owner_exiting(int ret, struct task_struct *exiting);
180
181/*
182 * Reflects a new waiter being added to the waitqueue.
183 */
184static inline void futex_hb_waiters_inc(struct futex_hash_bucket *hb)
185{
186#ifdef CONFIG_SMP
187 atomic_inc(&hb->waiters);
188 /*
189 * Full barrier (A), see the ordering comment above.
190 */
191 smp_mb__after_atomic();
192#endif
193}
194
195/*
196 * Reflects a waiter being removed from the waitqueue by wakeup
197 * paths.
198 */
199static inline void futex_hb_waiters_dec(struct futex_hash_bucket *hb)
200{
201#ifdef CONFIG_SMP
202 atomic_dec(&hb->waiters);
203#endif
204}
205
206static inline int futex_hb_waiters_pending(struct futex_hash_bucket *hb)
207{
208#ifdef CONFIG_SMP
209 /*
210 * Full barrier (B), see the ordering comment above.
211 */
212 smp_mb();
213 return atomic_read(&hb->waiters);
214#else
215 return 1;
216#endif
217}
218
219extern struct futex_hash_bucket *futex_q_lock(struct futex_q *q);
220extern void futex_q_unlock(struct futex_hash_bucket *hb);
221
222
223extern int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
224 union futex_key *key,
225 struct futex_pi_state **ps,
226 struct task_struct *task,
227 struct task_struct **exiting,
228 int set_waiters);
229
230extern int refill_pi_state_cache(void);
231extern void get_pi_state(struct futex_pi_state *pi_state);
232extern void put_pi_state(struct futex_pi_state *pi_state);
233extern int fixup_pi_owner(u32 __user *uaddr, struct futex_q *q, int locked);
234
235/*
236 * Express the locking dependencies for lockdep:
237 */
238static inline void
239double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
240{
241 if (hb1 > hb2)
242 swap(hb1, hb2);
243
244 spin_lock(&hb1->lock);
245 if (hb1 != hb2)
246 spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
247}
248
249static inline void
250double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
251{
252 spin_unlock(&hb1->lock);
253 if (hb1 != hb2)
254 spin_unlock(&hb2->lock);
255}
256
257/* syscalls */
258
259extern int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, u32
260 val, ktime_t *abs_time, u32 bitset, u32 __user
261 *uaddr2);
262
263extern int futex_requeue(u32 __user *uaddr1, unsigned int flags,
264 u32 __user *uaddr2, int nr_wake, int nr_requeue,
265 u32 *cmpval, int requeue_pi);
266
267extern int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
268 ktime_t *abs_time, u32 bitset);
269
270/**
271 * struct futex_vector - Auxiliary struct for futex_waitv()
272 * @w: Userspace provided data
273 * @q: Kernel side data
274 *
275 * Struct used to build an array with all data need for futex_waitv()
276 */
277struct futex_vector {
278 struct futex_waitv w;
279 struct futex_q q;
280};
281
282extern int futex_wait_multiple(struct futex_vector *vs, unsigned int count,
283 struct hrtimer_sleeper *to);
284
285extern int futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset);
286
287extern int futex_wake_op(u32 __user *uaddr1, unsigned int flags,
288 u32 __user *uaddr2, int nr_wake, int nr_wake2, int op);
289
290extern int futex_unlock_pi(u32 __user *uaddr, unsigned int flags);
291
292extern int futex_lock_pi(u32 __user *uaddr, unsigned int flags, ktime_t *time, int trylock);
293
294#endif /* _FUTEX_H */